Pulsed power has a number of military, industrial, and scientific applications. For example, the U.S. Department of Defense has been using a variety of pulsed power devices such as the Z accelerator at Sandia National Laboratory for emulating nuclear weapon effects and verifying computer models. The Z machine is said to serve as a model for a larger X-1 machine, which should provide enough X-ray energy and power to implode fusion capsules of deuterium and tritium to achieve high-yield fusion.
For most applications, a high-voltage capacitor bank is discharged for pulsed power production. Unfortunately, the energy storage density of a typical high-voltage capacitor is relatively low, especially if the capacitor is rated for repetitive operation. Moreover, a fast current rise is important for obtaining not only a high pulsed power level but also a high X-ray or neutron yield. A fast current rise requires high voltage and low inductance. (See, e.g., U.S. Pat. No. 4,446,096 issued May 1, 1984.)
Due to the limitations of capacitor banks, there has been considerable effort toward developing pulsed power generators using stored inductive energy. There are a number of relatively low cost electrical power sources that provide stored inductive energy and have a relatively high energy density. These electrical power sources include homopolar generators, compensated alternators, and explosively-driven magnetic flux compressors. An opening switch, however, is needed for obtaining pulsed power having a fast current rise from the stored inductive energy.
For example, to power a dense plasma focus with an explosive generator, a useful switch would interrupt a few megamperes in less than one microsecond and remain open for the 3 to 4 microsecond pulse delivered to the device. (Freeman et al., “Plasma Focus Experiments Powered by Explosive Generators,” LA-UR-83-1083, Los Alamos National Laboratories, Los Alamos, 1983, p. 13.)
Efforts toward development of a suitable opening switch are described in G. D. Roy, “High Power, High Repetition Rate Switches: An Overview,” Naval Research Review, Vol. 2, 1990, p. 17-24. Desired attributes of the switch are fast opening, fast recovery to achieve high repetition rates, controllable and long conduction time, low resistance during conduction, fast rise of impedance during opening, high impedance after opening, large currents, large stand-off voltage, and jitter-free operation. The plasma flow switch is mentioned as having conduction time up to 10−5 seconds and opening time in the 100 nanosecond time scale, and as of 1990, useful only in very high power (terrawatt), low impedance (10 ohm), single shot, staged pulsed power systems. (Page 19.)